Lower limb deficiencies

Lower limb deficienciesLower limb deficiencies are rare deformities. Management of lower limb deficiencies is complex, requiring correcting length equalization, stabilizing unstable joints, and correcting angular and rotational deformity. Prudent management requires a balanced approach, balancing cosmetic and functional outcomes against risks and costs of surgery.

Principles of Management

Diagnosis Establish an accurate diagnosis. Refer to a children’s limb deficiency clinic when available. Refer to a geneticist. Consider other problems.

Family distress Deal with the family’s shock and guilt. Be positive. Most children can have a relatively normal childhood and can become independent and productive adults.

Planning Plan a management strategy. Tailor the plan to address the unique deformities of the child and social values of the family.

Family preferences Be prepared to deal with the family’s preference to lengthening over amputation, even for deformities best managed by conversion and prosthetic fitting. Be prepared for the impact of the Internet, support groups, and input from other parents on decision making.

Support groups Encourage the family to discuss management with others in support groups and medical centers.

Growth Be prepared for the effect of growth.

Amputations This procedure is well-tolerated in children, but peer and family issues often complicate management.

Pain Children rarely have phantom pain after amputation.

Greater demands Children impose greater physical demands on prosthetics.

Dealing with Deformity

Preserve length and growth plates.

Stabilize the proximal joints when possible.

Save the knee joint if possible.

Complex Be prepared to deal with problems other than limb deficiency, as deformities are often complex.

Length Estimate roughly the anticipated magnitude of shortening at maturity to plan management.

Anticipate lengthening to roughly 20%–25% of the bone length with each lengthening.

Perform disarticulations rather than transosseous amputations when possible to prevent diaphyseal overgrowth.

Coordinate operative and prosthetic management thoughtfully.

Useful procedures include the Syme amputation (disarticulation of ankle); Boyd amputation (Syme amputation with preservation of calcaneus in the ankle mortis); knee disarticulation; modified Van Nes rotationalplasty; Brown procedure; and ankle fusion with or without other procedures.

Tibial Deficiency

Tibial deficiency is a congenital hypoplasia or aplasia of the tibia. Classify the deformity based on the extent of loss. This deficiency may be genetic. Refer to a geneticist for a consultation and counseling. Management is based on the adequacy of the upper tibial segment.

Adequate Upper Tibial Segment

Centralize the fibula under the tibia and disarticulate the ankle at about one year of age. Fit the child with a Syme prosthesis.

Inadequate Upper Tibial Segment

Best management is disarticulation of the knee and prosthetic fitting in late infancy or early childhood.

Femoral Deficiency

Congenital femoral deficiency (CFD) includes a spectrum of deformities that may be associated with fibular deficiency. Some divide the condition into proximal defects and defects that involve the shaft of the femur.

Natural History

The normal and abnormal sides remain proportionately the same throughout growth. The limb length inequality is the most obvious source of problems. Less obvious, but often significant, are hip and knee joint instability. Less significant is an external rotation deformity of the femur.

Deformity

PFFD includes a number of limb deformities. Consider each as part of general management.

Length Length is a major problem. Calculate the estimated discrepancy at maturity to guide management. Base the management decision on severity.

Hip joint Predict hip status based on the volume of the acetabulum. A poor acetabulum suggests that the hip will be unstable during lengthening. Mild degrees of dysplasia are correctable. Be aware that an unstable hip joint jeopardizes the success of femoral lengthening.

Proximal femur A bulbous shape of the upper femur suggests that the proximal femur is complete, but with a varus deformity and slow ossification. In contrast, a pointed and sclerotic upper femur suggests a more severe deficiency. Perform arthrography early to determine the pathology. Correct the varus early to enhance ossification. Congenital absence of the cruciate ligaments is common, and requires knee stabilization during femoral lengthening.

Timing of Correction

Correct proximal femoral deformity during the first year. Fit with temporary prosthesis by age 2 years. Staged lengthenings may be started as early as the second year. Delay rotationalplasties until about age 4 years.

Procedures

Hip fusion for PFFD is controversial. It provides stability for walking or lengthening procedures. It may, however, make prosthetic fitting more difficult than the unfused mobile but unstable hip.

Subtrochanteric osteotomy is indicated for correction of varus. When associated with delayed ossification of the proximal femur, fusion and correction are more difficult.

Rotationalplasty includes excision of the knee joint and rotation of the extremity 180°, allowing the child’s ankle to become the knee joint in the prosthesis. The procedure improves function but degrades appearance and is more suitable for males because clothing better hides the deformity.

Syme or Boyd amputation is indicated to allow prosthetic fitting with a knee disarticulation type of prosthesis. It is simple, cosmetic, and allows early prosthetic fitting, but at the cost of reduced efficiency.

Knee fusion is usually combined with Syme amputation to provide stability and to position the Syme stump just above the level of the opposite knee joint to facilitate prosthetic fitting.

Femoral lengthening may be considered for a congenital short femur expected to be 5–20 cm shorter than the opposite side at the end of growth. With increasing length gained, complications and risk of joint damage increase. Rapidly changing technology will undoubtedly increase feasibility of greater lengthening in the future.

Alternatives

Special situations such as bilateral deformity may make prosthetic management without conversion a desirable option.

Fibular Deficiency

This deformity is the most common of the lower limb deficiencies. It occurs sporadically and seldom has a genetic basis.

Pathology

There is partial or complete absence of the fibula. A fibrous analogue may replace the osseous fibula. Fibular shortening causes lateral ankle instability. Tibial deformities may include shortening, anterior bowing, and valgus deformity. Foot deformities include the absence of the lateral portions of the foot, talocalcaneal fusions, and ankle equinus.

Natural History

Shortening is progressive but remains proportionally shortened compared to the opposite, normal side. Ankle instability results in deformity and pain in the second decade. Knee valgus may cause disability. Disability from shortening is proportional to severity.

Management

Classify the type of deformity. Calculate roughly the expected shortening at skeletal maturation. Operative management is largely determined by the extent of foot deficiencies and ankle instability. Managing the deformity is often less difficult than effectively dealing with the family.

Dealing with the family Families often have difficulty accepting Syme amputation and prosthetic management, even for severe deformities. Families often wish to delay a decision in the hope that new technology will make amputation unnecessary, or delay until the child can participate in the decision. Families often use electronic communication with other families and may elect to visit centers where complex reconstructive procedures are offered. If the family cannot make a decision, provide a special prosthesis that can incorporate the foot while the decision is being made.

Operative management Plan amputation late in the first year just before the infant would normally stand and walk. Perform a Syme or Boyd procedure. The value of resection of the fibular analogue is controversial. Correct significant tibia vara to facilitate prosthetic fitting and walking. Lengthening is best delayed until midchildhood. A shoe lift may be necessary before lengthening. Make the lift light, least intrusive, and about one inch less in height than is necessary to level the pelvis.

Genu valgum is a common associated deformity. If significant, correct by a medial distal femoral stapling in late childhood or a distal femoral osteotomy.

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